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Operations were performed to cannulate the efferent duct of the popliteal node of sheep and, at the same time, the blood vascular system was removed surgically from the popliteal fossa so that the node was deprived of it blood supply. Twelve preparations were technically successful in that lymph flowed spontaneously from the unanaesthetised sheep for from 3 to 30 days after the operation. Eight control preparations were established in which the blood supply of the node with the cannulated efferent duct was left intact. In only four of the test preparations was the function of the node decisively impaired so that dendritic macrophages appeared in the lymph, the output of lymphocytes remained very low, and later histological examination showed the nodes to be grossly depleted of lymphocytes. In two of these four preparations the surgical devascularization of the node was aided by arterial embolization. In the remaining eight test preparations the outputs of lymphocytes in the lymph gradually regained normal values, and the nodes then responded normally to antigenic stimuli.

Individual lymph nodes of sheep were perfused, via a cannula in one of their afferent lymphatics, with a variety of toxic materials. This procedure was designed to ablate the parenchyma of the nodes so that the macrophage-rich afferent lymph would pass unaltered into the efferent duct, which also had been cannulated. Although many materials caused transient inflammation and/or immunoblastic responses, few caused lasting alterations in the cellular composition of the efferent lymph. Only melphalan, an alkylating agent, succeeded in damaging the internal structure of the nodes so that true afferent lymph appeared in the efferent duct and abundant dendritic macrophages could be collected. In the doses necessary to achieve this enough of the melphalan became systematized to produce a transient alopecia.